1. Field of the Invention
The invention relates to an inkjet head, and more specifically, to mounting and configuration of an inkjet head nozzle used for the inkjet head.
2. Background Art
In association with proliferation of personal computers and progress in graphic processing programs, an output of a hard copy having a high image quality as well as an output of a character have come to be required in connection with inkjet printing. In the field of printing of a signboard or a large-sized poster, many on-demand print requests are issued. For these reasons, an on-demand inkjet recording apparatus has been frequently used.
An inkjet head used in the on-demand inkjet recording apparatus is roughly divided into three types. Namely, a first type of inkjet head is a so-called thermal jet inkjet head which is equipped with a heater for momentarily vaporizing ink disposed at the extremity of a nozzle, thereby producing and ejecting an ink droplet by means of expansion pressure derived from vaporization. A second type of inkjet head is an inkjet head utilizing shear-mode deformation of a piezoelectric element, wherein a container for forming an ink puddle section is equipped with a piezoelectric element which becomes deformed in accordance with a signal, and wherein an ink droplet is ejected by means of pressure derived from deformation. A third type of inkjet head is an inkjet head where in a piezoelectric element is disposed so as to oppose a pressure generation chamber formed from an ink puddle section, and an ink droplet is ejected by inducing dynamic pressure in the pressure generation chamber by means of contraction and extraction of the piezoelectric element. Electrostatic absorption is utilized in place of a piezoelectric element.
In the on-demand inkjet head of the third type, a plurality of nozzle orifices are arranged in a row on a chamber plate, and a plurality of plates are stacked to constitute an ink chamber. A piezoelectric element is mounted so as to oppose the ink chamber, and an ink droplet is ejected by utilization of deformation of the piezoelectric element (see e.g., JP-A-6-8422).
In the case of the inkjet head, when a nozzle packaging density, that is, a pitch between nozzles, has become small, the pitch between the ink chambers eventually becomes smaller, along with the piezoelectric element. To prevent such a reduction in pitch or size, nozzles are arranged in a plurality of rows within a head, and nozzles of the respective rows are offset from each other, thereby attempting to increase a print density which can be achieved by one scanning operation (see, e.g., JP-A-2000-289233). However, a plurality of rows of nozzles are provided in one plate, and hence piezoelectric transducers must also be formed for respective rows of nozzles so as to oppose the nozzles, because the piezoelectric transducers oppose nozzles when packaged.
FIG. 10 shows another related-art example of means for increasing the packaging density of nozzles. FIG. 10 is a schematic plan view showing a state in which a nozzle plate 101 has a plurality of nozzle orifices 100, a state of a chamber plate 103 in which the pressure generation chambers 102 are alternately arranged thereon in a staggered arrangement with respect to the nozzle orifices 100 arranged on the nozzle plate 101, and a state in which a piezoelectric element 150 divided in a comb-shaped pattern are fixed so as to oppose a pressure generation chamber 102 sealed with a diaphragm 104. In the case of such a configuration, since the pressure generation chambers 102 are arranged in a staggered arrangement, the corresponding piezoelectric elements 15 are also arranged in a staggered arrangement. Specifically, two groups of piezoelectric elements located very close to each other must be inserted and fixed with superior accuracy. Therefore, there arises a problem of poor ease of assembly.
In some inkjet heads, a silicon monocrystal substrate is taken as a constituent member, and nozzles formed in one surface of the silicon monocrystal substrate and those formed in the other surface are arranged in a staggered pattern within a single plane made by slicing a predetermined position on the silicon monocrystal substrate (see, e.g., JP-A-6-8449). In this case, the nozzle orifices, the pressure chambers, and restrictors are formed simultaneously in the silicon monocrystal substrate. Hence, the nozzle orifices formed in both surfaces of the substrate must assume a staggered arrangement.